A computer desk for bifocal lens wearers, with special emphasis on selected telecommunication tasks

Abstract

A computer desk was designed and built which allowed sinking and tilting the monitor axis to coincide with the vision axis of when looking through the reading portion of a bifocal glass. Ten subjects (four males and six females) wore a glass frame appropriately fitted whose distance vision portion was blocked with cardboard leaving reading portion cut out for clear vision. Such subjects worked with computer with its monitor placed in one of the three positions: (a) monitor sunken and backward inclined by 35°; (b) monitor placed on desk top level and horizontal; and (c) monitor placed horizontal but raised by CPU beneath it. Postural details of head-neck inclination, torque due to it, angle of gaze, angular span of vision, and upper extremity was recorded by photography. EMG of trapezius and sternomastoid was recorded bilaterally. Subjective discomfort rating was obtained using visual analog scale and Borg's scale. The head-neck inclination and torque were highest with sunken monitor, but it recorded 30% to 40% less EMG compared to raised monitor. Upper extremity postures were not significantly different between the monitor positions. The discomfort rating was in ratio of 1:2:4 for sunken, level, and raised monitors respectively.